Abstract: A magnetic tape drive includes a head assembly with a write head and a read head. The read head is positioned ahead of the write head, so that as a magnetic tape is moved across the head, the read head is able to read data that is about to be overwritten by the write head. When a client computer system commands the tape drive to write data to the magnetic tape, the tape drive writes the data to the tape but preserves any data that is overwritten by reading the data before it is overwritten. The preserved data is returned to the client computer system. In various examples, the returned data can be written back to the tape, discarded, or stored elsewhere under the control of the client computer system.

Abstract: A tape drive allows for an increased track density by partially overlapping adjacent tracks as each successive track is written. Each successive track overwrites a portion of the width of the previous track, thereby reducing the width of the previous track. This process can be applied repeatedly thereby producing an arrangement of shingled data tracks across the width of the tape. In an embodiment, single-pass verification of data written in this manner is accomplished using a head assembly with two read heads per track. A first read head positioned behind the write head verifies that the data written is correct, and a second read head positioned over the previous track verifies that data on the previous track remains intact after being partially overwritten.